Odd emails sent from my email address

One person whom I have previously emailed a few times has reported receiving some odd emails purporting to come from me that obviously do not. I believe they suggest following a link that might be of interest. I've received one or two like this myself, from my sister in Australia, and deleted them. Nobody else has complained, and I have not received any undeliverable notifications suggesting my account is sending large volumes of spam. I have changed my password and done a full system virus scan, which found nothing, but is there anything else I should be doing? Is it not possible that the emails are originating elsewhere and my address is simply being used to cover the sender's tracks? (Anyone can easily do that.) Even that the whole thing arises from someone else's email being hacked? I really don't want all the work of changing my email address if this is not necessary.